Fort Worth weekly gazette. [volume] (Fort Worth, Tex.) 1882-1891, 1887-05-06
IRON CRYSTALLIZATION.
Changes in the Fibre of Metal Which
Impossible to Detect. 81
PhiladeIphia Record.

Philadelphia Record. M
Since Il passenger train on the North
British RsilwaN plunged from the great
iron bridge over The Firth Of Tay into the
dark waters Below one stormy Decem-
Der night seven yeats ago, carrying every
living soul upon st to certain death,
there has been no rEiIroad bridge disaster
that has excitad so much public atten-
ton as that which recently occurred on
the Boston aud Providence Railroad at
the Bussey bridge, near Boston. In both,
the cause appears to have been struc-
tural defect. This may also be said OF
the Ashtabuls accident, whose horrors,
however, were Increased by the fierce
work OF flames and the inclemencies of
bitterly cold swinternight.
Bridge acGsdentstare considered by all
railroad men as ih3comparably the worst
to which travel by reil is exposed, and as
among the most difficult to guard against
absolutely. one source of danger was
Eahown In Wednesdays Record, when
the peonliaf effects of locomotives
hammer elbows upon a track were ex-
planned The theory was advanced that
girder Of. the bridge had broken be-
meath the engines drivers, whose pound
ing upon the effectively constructed
bridge was thus primarily the cause OF
the a6cident This brings up phase OF
RAILROAD and bridge accidents which is at
present receiving great deal of atten-
| ton Decentralization in the material Oh
l,iron Esid IS is an element Of danger now
SO wsArecognized tnat the Pennsylvania
RailfDkd Company has adopted the
Hefnitspolicy of substituting stone for
ron bridges, and the same plan is being
l1oilowedsBs other railroad companies.
e. The Lifetime of an iron bridge is from
ttWenty to twenty-five years, and consta1A
tcare is necessary to insure its safety. The
Ashtabula bridge was thirteen years old,
and at the time it fell beneath the weight
of two engines and heavy express train
the theory was commonly advanced that
crystallization had impaired its original
strength. The two great @meg
ing causes OF capitalization are
fbration and the hammer
blow of the locomotive, which gradually,
by repeated impact, turn the fibre of iron
or steel into q mass of crystals, needing
only some unusual pressure blow
to cause them to break apart. AddstO
this the oscillation caused by the passage
of trains at high rate of speed and Il
will be seen that an iron bridge isSxposeG
to peculiar perils, which can only be
guarded against by rigid inspection aid
constant renewals.
THE OPINION OF DIsTINGE ESGI
Capitalization was one of the Several
theories advanced by Park Benjamin, {
New York engineer, to account for TIT
Tay bridge accident. HesaiaG:
General indications goto show that thu
cause must be sought In an abnorma
condition of the structure, or rather one
which did not enter into the calculations
of the builders. 6Such a condition would
be the deterioratfln Of the metal by it
} hchange from fbrous to a crystalline
II state undeH repeated vibration Tha
/ this occurssfn railway bridges has beer
Vigorously disputedsby many well-knowI
e1tgsaeefs. On the OTHER hans many ex'
J aIhples are quoted by dfnefent authori-
ties to support the theory. Apropos tt
II this particular accident, distinguished
Z French engineer and iron founder now il
, this country informs US that he has known
8 bars Of iron made by himself from Scotch
pig to change from tough tibrous to
e brittle crystalline structure in travelling
} by rail only from the north Of France t
Paris. This is, of course, an extreme 10
: stance.
< Again, recent research has demon
e strated that because a structure with
2 stands large quiescent load that fact i
f little proof of stability under repeate
e shocks and vibrations. Metals are be
:, lieved TO have ''life." bar, for 'ez
j ample, may stand million vibration
D and break down at the million and irst
( and yet the last shock may be lighte
q than preceding ones. Attempts, however
e to REFUGE this law to practical applicatlo
r have elected an abundance of confictin
: evidence; but, nevertheless, it is we
0 settled that in no department {
2 mechanics is an extended course {
n actual experimenting more urgent
e needed or of graver public Importance
r STRENGTH OF THE TAY BRIDGE.
The strength of the Tay bridge at th
e time of It's building was pronounced ''pe.
e haps the most remarkable structure